Traditional helicopter control system employ a cyclic stick for pitch and roll control, pedals for yaw control, and a collective stick for lift control. Commonly-owned U.S. Pat. No. 4,420,808 (Diamond, et al, 1983) discloses a single sidearm controller (control stick) that provides control signals in each of the pitch, roll, yaw, and collective/lift axes of a helicopter control system. The stick is essentially a "force" stick in that there is limited displacement of the stick in each axis. Thus, there is little tactile feedback from the stick to the pilot as to the severity of a maneuver.
Studies have shown that under high vertical workload tasks, such as nap-of-the-earth (NOE) flight operations, the pilot cannot accurately perceive the extent of his collective input without diverting attention to a cockpit display (torque or collective position indicators). Proprioceptive cues are adequate for yaw and cyclic maneuvers, as the aircraft's agility is nearly instantaneous (little energy is required). The aircraft's lift (z-axis) response, however, necessitates a substantial change in energy state and is characterized by a long time constant.